Bold, aggressive style and awesome performance. This 4 port design has no downward facing ports which helps eliminate dust problems when shooting in the prone position. The Annihilator Muzzle Brake Maintains the aggressive styling that was so popular with the original Annihilator Flash Hider. It is made from 41L40 Heat Treated Steel RC 26-34. It is threaded 1/2"-28 and includes the crush washer.